Broadband providers (e.g., cable, satellite, DSL or fiber-optic-to-home providers) often deliver a real-time broadcast of a digital video multicast data stream (video stream) to subscribers over an internet protocol (IP) network. The video stream may include a real-time broadcast digitally encoded from an analog broadcast feed or program files already encoded in a digital format. When video is streamed, the incoming video stream is buffered at a subscriber's receiving device such as a set-top box or decoder. The buffer is continually emptied of data, decoded, and presented to the subscriber via a presentation device such as a TV. In the mean time, more data is received by the receiving device which refills the buffer, so there is a smooth presentation of data images on the screen of the presentation device.
Predominantly, the video streams are delivered to subscribers' receiving devices using digital video compression and transmission formats from a standard body known as the Moving Picture Experts Group (MPEG), although there are other types video compression and transmission formats (such as H.264). The video stream configured by the MPEG standard typically includes different types of frames, relationships between frames, and a prescribed order of the different types of frames.
The video stream is received by the receiving device (e.g., decoder) located at a subscriber's premises, which decodes the frames of the video stream so it can be displayed on the screen of a presentation device. To reduce bandwidth there are only a limited number of a particular types of frames, known as access points, in a video stream which allow decoders to decode a video stream after the decoder initially joins an incoming video stream. Unfortunately, a decoder must wait for these limited numbers of access points to arrive and then be decoded, before the decoder is able to display the first pictures of the video stream on the screen of a presentation device.
This is problematic for subscribers when they make a channel change request usually via a remote control, because there is a delay period experienced by the subscriber between the time the subscriber makes a channel change request and the subscriber is first presented with the first image of a frame of the video stream associated with the channel requested. During this delay period the screen of a presentation device is usually blank other than programming information. This phenomenon is known as a “channel change delay.” This delay has grown from milliseconds to seconds with the current generation of new video delivery technology. Accordingly, channel change delay, which was once unnoticed, has increased to the point that viewers of video broadcasts received over IP distribution systems are unable to channel surf effectively without experiencing annoying delay periods.
Thus, there is an unsolved need to adequately reduce channel change delays that often occur when subscribers change channels in a video broadcast over IP network environment.